The goals of this project are to delineate some of the synthetic mechanisms and control mechanisms involved in E. coli DNA replication. One major goal is to define the strand specificity of the two discrete size classes of small DNA intermediates generated during discontinuous DNA synthesis. Experiments designed to determine the specific DNA intermediates synthesized in concert with, as well as opposite to, the direction of replication fork progress are also planned. Genetic fine structure mapping of the dnaB gene using overlapping deletions is a companion to these experiments. Genetic and biochemical experiments on the control of initiation of chromosome replication are also planned. The biochemical phase of these experiments utilizes our recently devised in vitro initiation assay to examine the biochemical processes required to initiate synthesis at the origin. A series of companion experiments to investigate the specificity of the initiation process for particular origins are currently in progress.